Rheological characterization of Poloxamer 407 hydrogels

Abstract

Introduction: The rheological profile of a semi-solid product is one of the quality parameters and allows to determine the changes in the viscosity of the product with changing temperature [1]. Poloxamer 407 (P407) aqueous solutions show a temperature-dependent liquid-gel transition [2]. The gelation temperature (Tgel) is influenced by P407 concentration [3]. The aim of this study was to evaluate the dependence of rheological behavior on the concentration of P407 in the hydrogel. Materials and methods: P407 concentration in hydrogels was in the range of 15%–25%. Eight compositions of hydrogel were generated applying the experimental design of the response surface. Poloxamer 407 was solubilized in the purified water at +4 °C for 24 hours. Temperature test (cooling from 37 ºC to 4 ºC at 1 ºC/min) and flow curve (at 20 ºC) were performed with a model MCR102 rotational rheometer (Anton Paar, Austria) equipped with a plate-plate geometry and Peltier temperature controlled system. Results: Our data revealed that the Tgel decreased from 28 ºC to 17 ºC following the increase of the P407 concentration from 15% to 25%. The effect of shear rate on the consistency coefficient (κ) and flow behavior index (n) can be established by the Power law model. It has been previously established that the κ values represent the viscosity of the semi-solid product. The value of consistency coefficient (κ) increases from 0,0198 to 341,82 with increasing poloxamer 407 concentration in the hydrogel. Flow behavior index values of hydrogels decreased from 1,0546 to 0,03922 following the increase of the P407 concentration. Newtonian fluids are known to exhibit flow behavior index values equivalent to 1 and as the value approaches zero the material is known to be non-Newtonian. It was found that 15% and 17% concentration P407 hydrogels are liquids at 20 ºC and the higher concentration of P407 allowed forming hydrogels. Conclusions: The Tgel and the flow behavior are important..